Information codes such as two-dimensional codes have now been used in many applications. Such applications include an application in which a picture or a figure is arranged in the code area. For example, a technique provided by patent literature 1 is concerned with a two-dimensional code produced by strings of reverse-converted bits is obtained which bits are reversely converted from strings of bits. These strings of bits form the region of the code, in which the region is composed of a single level. The reverse-converted bit strings are converted based on information about a format for the two-dimensional code, thus producing a unique two-dimensional code with a design region composed of the single gray level.